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package com.sun.mail.imap;

import java.io.*;
import javax.mail.*;
import com.sun.mail.imap.protocol.*;
import com.sun.mail.iap.*;
import com.sun.mail.util.*;

/**
 * This class implements an IMAP data stream.
 * 
 * @author John Mani
 */

public class IMAPInputStream extends InputStream {
	private IMAPMessage msg; // this message
	private String section; // section-id
	private int pos; // track the position within the IMAP datastream
	private int blksize; // number of bytes to read in each FETCH request
	private int max; // the total number of bytes in this section.
	// -1 indicates unknown
	private byte[] buf; // the buffer obtained from fetchBODY()
	private int bufcount; // The index one greater than the index of the
	// last valid byte in 'buf'
	private int bufpos; // The current position within 'buf'
	private boolean lastBuffer; // is this the last buffer of data?
	private boolean peek; // peek instead of fetch?
	private ByteArray readbuf; // reuse for each read

	// Allocate this much extra space in the read buffer to allow
	// space for the FETCH response overhead
	private static final int slop = 64;

	/**
	 * Create an IMAPInputStream.
	 */
	public IMAPInputStream(IMAPMessage msg, String section, int max, boolean peek) {
		this.msg = msg;
		this.section = section;
		this.max = max;
		this.peek = peek;
		pos = 0;
		blksize = msg.getFetchBlockSize();
	}

	/**
	 * Do a NOOP to force any untagged EXPUNGE responses
	 * and then check if this message is expunged.
	 */
	private void forceCheckExpunged() throws MessageRemovedIOException, FolderClosedIOException {
		synchronized (msg.getMessageCacheLock()) {
			try {
				msg.getProtocol().noop();
			} catch (ConnectionException cex) {
				throw new FolderClosedIOException(msg.getFolder(), cex.getMessage());
			} catch (FolderClosedException fex) {
				throw new FolderClosedIOException(fex.getFolder(), fex.getMessage());
			} catch (ProtocolException pex) {
				// ignore it
			}
		}
		if (msg.isExpunged())
			throw new MessageRemovedIOException();
	}

	/**
	 * Fetch more data from the server. This method assumes that all
	 * data has already been read in, hence bufpos > bufcount.
	 */
	private void fill() throws IOException {
		/*
		 * If we've read the last buffer, there's no more to read.
		 * If we know the total number of bytes available from this
		 * section, let's check if we have consumed that many bytes.
		 */
		if (lastBuffer || max != -1 && pos >= max) {
			if (pos == 0)
				checkSeen();
			readbuf = null; // XXX - return to pool?
			return; // the caller of fill() will return -1.
		}

		BODY b = null;
		if (readbuf == null)
			readbuf = new ByteArray(blksize + slop);

		ByteArray ba;
		int cnt;
		// Acquire MessageCacheLock, to freeze seqnum.
		synchronized (msg.getMessageCacheLock()) {
			try {
				IMAPProtocol p = msg.getProtocol();

				// Check whether this message is expunged
				if (msg.isExpunged())
					throw new MessageRemovedIOException("No content for expunged message");

				int seqnum = msg.getSequenceNumber();
				cnt = blksize;
				if (max != -1 && pos + blksize > max)
					cnt = max - pos;
				if (peek)
					b = p.peekBody(seqnum, section, pos, cnt, readbuf);
				else
					b = p.fetchBody(seqnum, section, pos, cnt, readbuf);
			} catch (ProtocolException pex) {
				forceCheckExpunged();
				throw new IOException(pex.getMessage());
			} catch (FolderClosedException fex) {
				throw new FolderClosedIOException(fex.getFolder(), fex.getMessage());
			}

			if (b == null || ((ba = b.getByteArray()) == null)) {
				forceCheckExpunged();
				throw new IOException("No content");
			}
		}

		// make sure the SEEN flag is set after reading the first chunk
		if (pos == 0)
			checkSeen();

		// setup new values ..
		buf = ba.getBytes();
		bufpos = ba.getStart();
		int n = ba.getCount(); // will be zero, if all data has been
		// consumed from the server.
		// if we got less than we asked for, this is the last buffer of data
		lastBuffer = n < cnt;
		bufcount = bufpos + n;
		pos += n;
	}

	/**
	 * Reads the next byte of data from this buffered input stream.
	 * If no byte is available, the value <code>-1</code> is returned.
	 */
	public synchronized int read() throws IOException {
		if (bufpos >= bufcount) {
			fill();
			if (bufpos >= bufcount)
				return -1; // EOF
		}
		return buf[bufpos++] & 0xff;
	}

	/**
	 * Reads up to <code>len</code> bytes of data from this
	 * input stream into the given buffer.
	 * <p>
	 * 
	 * Returns the total number of bytes read into the buffer, or
	 * <code>-1</code> if there is no more data.
	 * <p>
	 * 
	 * Note that this method mimics the "weird !" semantics of
	 * BufferedInputStream in that the number of bytes actually returned may be
	 * less that the requested value. So callers of this routine should be aware
	 * of this and must check the return value to insure that they have obtained
	 * the requisite number of bytes.
	 */
	public synchronized int read(byte b[], int off, int len) throws IOException {

		int avail = bufcount - bufpos;
		if (avail <= 0) {
			fill();
			avail = bufcount - bufpos;
			if (avail <= 0)
				return -1; // EOF
		}
		int cnt = (avail < len) ? avail : len;
		System.arraycopy(buf, bufpos, b, off, cnt);
		bufpos += cnt;
		return cnt;
	}

	/**
	 * Reads up to <code>b.length</code> bytes of data from this input
	 * stream into an array of bytes.
	 * <p>
	 * 
	 * Returns the total number of bytes read into the buffer, or
	 * <code>-1</code> is there is no more data.
	 * <p>
	 * 
	 * Note that this method mimics the "weird !" semantics of
	 * BufferedInputStream in that the number of bytes actually returned may be
	 * less that the requested value. So callers of this routine should be aware
	 * of this and must check the return value to insure that they have obtained
	 * the requisite number of bytes.
	 */
	public int read(byte b[]) throws IOException {
		return read(b, 0, b.length);
	}

	/**
	 * Returns the number of bytes that can be read from this input
	 * stream without blocking.
	 */
	public synchronized int available() throws IOException {
		return (bufcount - bufpos);
	}

	/**
	 * Normally the SEEN flag will have been set by now, but if not,
	 * force it to be set (as long as the folder isn't open read-only
	 * and we're not peeking).
	 * And of course, if there's no folder (e.g., a nested message)
	 * don't do anything.
	 */
	private void checkSeen() {
		if (peek) // if we're peeking, don't set the SEEN flag
			return;
		try {
			Folder f = msg.getFolder();
			if (f != null && f.getMode() != Folder.READ_ONLY && !msg.isSet(Flags.Flag.SEEN))
				msg.setFlag(Flags.Flag.SEEN, true);
		} catch (MessagingException ex) {
			// ignore it
		}
	}
}
